1. Purpose of the Invention
This invention relates in general to certain new and useful improvements in propeller and impeller constructions, and, more particularly, to propeller and impeller constructions having blades of unique cross-sectional shape and configuration and which provide a unique mounting to a wide variety of structures.
2. Brief Description of the Prior Art
For many years, considerable study has been devoted to improving various aerodynamic structures, as for example, wind machines, aircraft and the like, in order to improve their efficiency. Conventional aerodynamic theory is based primarily on Bernoulli's Theorem and very little theory in airfoil design has changed since the early 1900's, except for the addition of flaps and slots on components which are driven through a gaseous (air) or through a liquid fluid. Considerable experimentation by F. G. Miles of Great Britain has been underway since about 1938 on boundary layer control, enforced circulation and pressurized air flow. This experimentation has been devoted to experiments to determine the results of "sucking and blowing" around an airfoil.
However, substantially all of the experimentation dealing with conventional aerodynamic theory seems to be confined to wing structures on conventionally styled aircraft, and little, if any, work has been conducted in the area of applying various aerodynamic theories to propeller or impeller design.
It has generally been believed that the geometric arrangement providing best aerodynamic efficiency for impellers and propellers is one that becomes well suited to a slender, thin, moderately twisted, metal extrusion. See, for example, U.S. Pat. No. 2,985,245 to Maloff.
In the conventional propeller and impeller design, a thrust is produced by the action of the impeller or propeller blades on the air which is propelled or impelled. This thrust is directly related to the change in energy level of the air passing with respect to the blades. Hence, one of the major problems presented is that the change in energy levels must be restrained by balancing out the reacting forces in the blades. Another one of the major problems encountered is the mounting of the blades to a central rotating hub. The conventional geometry of the slender, thin, twisted, metal extruded blade creates large bending moments in the region of the hub, and these bending moments may actually exceed the tension stresses caused by centrifugal force.
The development of the propeller driven aircraft has been accompanied by increased applications for large diameter propeller fans, impellers, rotors, and the like. Basic design for such devices has been largely restricted to blades where the cross sections thereof resemble airfoils of a type providing a high lift/drag ratio and are similar in shape to the cross section of aircraft wings.
Propeller fans of this type have cross sections which are commonly found in applications such as cooling towers, large ventilating fans and wind machines used for frost protection. These fans are generally heavy in weight and require a massive and inefficient hub section and are difficult and costly to manufacture.
The design of these devices is generally based on considerations of "lift vs. drag" ratios rather than the more pertinent "mass flow rate vs. energy expended" ratio. The dependence on constructions based primarily on conventional propellers and airfoils, for applications relating to what can be described as fixed position fans, has ignored the needs for economies of manufacturing, economies of operation and overall improvements in performance in those applications. Such constructions have ignored the needs of industry outside of the aerospace industry for a fan construction that features low cost, noise suppression and energy conservation.